Field of the Invention
The present invention relates to a method for applying a substance, in particular a developer, to a surface. The present invention also relates to an apparatus for performing the method of the invention.
In the production of integrated semiconductor products, process steps often arise in which a substance must be applied to the surface of a semiconductor wafer. Particularly in the structuring of the wafer surface by a phototechnique, a developer fluid must be applied to an exposed photoresist, in order for a latent image created by illumination to be developed in the photoresist.
However, in the wet chemical developer process of photoresists, the nonhomogeneity with which the developer is applied causes fluctuations in the widths of resist structures, and they are transferred directly to the substrate to be etched. That causes a fluctuation in the structural dimensions within a chip and from one chip to another, and those fluctuations can, for instance, lead to different electrical parameters of the integrated circuits, or even the failure of an integrated circuit.
Since resist thickness fluctuations can lead to differences in electrical parameters of the integrated circuits as well as to the failure of an integrated circuit as already noted, certain resist and etching thickness limits are prescribed, so that the integrated circuit can be produced in functional, reliable form. In order to adhere to those limits and minimize rework rates in lithography, it is therefore necessary to optimize the developer process in such a way that resist thickness fluctuations caused by the developer application can be reduced.